fs: only specify I_DIRTY_TIME when needed in generic_update_time()

generic_update_time() always passes I_DIRTY_TIME to
__mark_inode_dirty(), which doesn't really make sense because (a)
generic_update_time() might be asked to do only an i_version update, not
also a timestamps update; and (b) I_DIRTY_TIME is only supposed to be
set in i_state if the filesystem has lazytime enabled, so using it
unconditionally in generic_update_time() is inconsistent.

As a result there is a weird edge case where if only an i_version update
was requested (not also a timestamps update) but it is no longer needed
(i.e. inode_maybe_inc_iversion() returns false), then I_DIRTY_TIME will
be set in i_state even if the filesystem isn't mounted with lazytime.

Fix this by only passing I_DIRTY_TIME to __mark_inode_dirty() if the
timestamps were updated and the filesystem has lazytime enabled.

Link: https://lore.kernel.org/r/20210112190253.64307-4-ebiggers@kernel.org
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Jan Kara <jack@suse.cz>

diff --git a/fs/inode.c b/fs/inode.c
index 6442d97..d0fa43d 100644 (file)
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -1743,24 +1743,26 @@ static int relatime_need_update(struct vfsmount *mnt, struct inode *inode,
 
 int generic_update_time(struct inode *inode, struct timespec64 *time, int flags)
 {
-       int iflags = I_DIRTY_TIME;
-       bool dirty = false;
-
-       if (flags & S_ATIME)
-               inode->i_atime = *time;
-       if (flags & S_VERSION)
-               dirty = inode_maybe_inc_iversion(inode, false);
-       if (flags & S_CTIME)
-               inode->i_ctime = *time;
-       if (flags & S_MTIME)
-               inode->i_mtime = *time;
-       if ((flags & (S_ATIME | S_CTIME | S_MTIME)) &&
-           !(inode->i_sb->s_flags & SB_LAZYTIME))
-               dirty = true;
-
-       if (dirty)
-               iflags |= I_DIRTY_SYNC;
-       __mark_inode_dirty(inode, iflags);
+       int dirty_flags = 0;
+
+       if (flags & (S_ATIME | S_CTIME | S_MTIME)) {
+               if (flags & S_ATIME)
+                       inode->i_atime = *time;
+               if (flags & S_CTIME)
+                       inode->i_ctime = *time;
+               if (flags & S_MTIME)
+                       inode->i_mtime = *time;
+
+               if (inode->i_sb->s_flags & SB_LAZYTIME)
+                       dirty_flags |= I_DIRTY_TIME;
+               else
+                       dirty_flags |= I_DIRTY_SYNC;
+       }
+
+       if ((flags & S_VERSION) && inode_maybe_inc_iversion(inode, false))
+               dirty_flags |= I_DIRTY_SYNC;
+
+       __mark_inode_dirty(inode, dirty_flags);
        return 0;
 }
 EXPORT_SYMBOL(generic_update_time);